Processing and Presentation of Minor Histocompatibility Antigens that Cause GvHD

次要组织相容性(H)抗原(AGS)在移植物抗宿主免疫发病机制中起不利作用 即使在接受了人类白细胞抗原相合的骨髓移植的患者中，也会发生移植物抗宿主病。在这里，收件人次要H AGS是 由供体抗原提呈细胞(APC)获得，并由MHC I类分子加工和提呈 在一个被广泛研究的过程中被称为交叉呈递，或者被II类分子在一个较少被理解的过程中 称为间接呈现。在实体器官移植环境中，间接陈述需要获取， 由受者的APC处理和呈递供体同种异体抗原。在肿瘤和微生物方面 AGS，一种II+APC-比作受体细胞-获得驻留在II类阴性细胞中的Ag-比作 供体细胞-处理并将其呈递给同源的CD4+(T)细胞。我们对间接的机械研究 H 演示文稿显示，雄性PHY和李斯特菌来源的pLLO AGS在通过 接收的APC获得了细胞质溶质。在这里，PHY的间接表示是 免疫蛋白酶体依赖的TAP(胞浆到ER的多肽转运体)和ERAAP(ER相关的 氨基肽酶)不依赖。令人惊讶的是，TAP和ERAAP都转移或摧毁了PHY和pLLO 从而减少了它们对TH细胞的呈现。这些发现引出了两个关键问题：(A)I班 全球银加工(CAP)机械影响第二类限制的银提呈；和(B)胞质如何 AGS能接触到内切/溶酶体以间接呈现吗？在试图理解细胞质是如何 PHY返回到内切/溶酶体来呈现，我们排除了宏观自噬作为间接的作用 HY的出现是在树突状细胞条件性缺失ATG5的小鼠身上进行的。相反，我们 发现同源二聚体TAP-样(TAP-L)是一种不同于内质网的孤儿内切/溶酶体肽转运体。 需要常驻TAP1/TAP2-以间接呈现PHY。基于我们的功能研究，在这里， 我们寻求获得对间接呈现机制的生物化学见解(S)。因此，我们将测试中央 假设I类Ag加工机械调节某些胞质AGs池可供 第II类--限制间接陈述。这种AGs在胞浆中被加工，并被运输到Endo/ 溶酶体在TAP-L依赖的机制中。为了检验这一假设，我们将(A)确定CAP是否 机械在全球范围内影响自身或微生物来源的胞浆的H_2Ab限制的处理和呈现 AGS；(B)确定胞质AGS如何进入内切/溶酶体进行间接提呈；以及(C)确定 CAP机制是否影响胞浆内抗原特异性的CD4+T细胞库。成功完成这项工作 这项工作将产生新的生化洞察力(S)，以间接的第二类分子的银提呈。机械师 了解第II类限制的间接银呈递不仅对于开发 避免/治疗GvHD，但也用于疫苗设计，因为这一过程在胞浆呈现时是可操作的 AGS(病毒、细菌、寄生虫)对TH细胞，因此，用于针对肿瘤和病原体的疫苗设计。好了！

Minor histocompatibility (H) antigens (Ags) play a detrimental role in the immunopathogenesis of graft-vs-host disease (GvHD) even in recipients of HLA identical bone marrow transplants. Herein, recipient minor H Ags are acquired by donor Ag-presenting cells (APCs) and processed and presented either by MHC class I molecules in a well studied process termed cross-presentation or by class II molecules in a less well understood process called indirect presentation. In a solid organ transplant setting, indirect presentation entails the acquisition, processing and presentation of donor alloantigens by the recipient's APCs. In the case of tumour and microbial Ags, a class II+ APC-likened to a recipient cell-acquires the Ag residing in a class II-negative cell-likened to a donor cell-and processes and presents it to cognate CD4+ (T ) cells. Our mechanistic studies into indirect H presentation revealed that the male pHY and Listeria monocytogenes-derived pLLO Ags upon acquisition by the recipient APCs gained access to the cytosol. Herein, the indirect presentation of pHY was immunoproteasome-dependent yet TAP (cytosol to ER peptide transporter)- and ERAAP (ER-associated amino-peptidase)-independent. Surprisingly, both TAP and ERAAP either diverted or destroyed pHY and pLLO thereby reducing their presentation to TH cells. These finding led to two critical questions: (a) does the class I Ag processing (CAP) machinery globally impact class II-restricted Ag presentation; and (b) how do cytosolic Ags gain access to the endo/lysosomes for indirect presentation? In trying to understand how the cytosolic pHY returned to the endo/lysosomes for presentation, we ruled out the role for macro-autophagy as indirect presentation of HY proceeded in mice in which dendritic cells were conditionally deficient for Atg5. Instead, we found that the homodimeric TAP-like (TAP-L)-an orphan endo/lysosomal peptide transporter distinct from ER- resident TAP1/TAP2-was needed for indirect pHY presentation. Predicated on our functional studies, herein, we seek to gain biochemical insights into indirect presentation mechanism(s). Hence, we will test the central hypothesis that the class I Ag processing machinery regulates the pool of certain cytosolic Ags available for class II-restricted indirect presentation. Such Ags are processed in the cytosol and transported to the endo/ lysosomes in a TAP-L-dependent mechanism. To test this hypothesis, we will (a) determine whether the CAP machinery globally impacts H2Ab-restricted processing and presentation of self- or microbe-derived cytosolic Ags; (b) determine how cytosolic Ags enter the endo/lysosomes for indirect presentation; and (c) determine whether the CAP machinery impacts cytosolic Ag specific CD4+ T cell repertoire. Successful completion of this work will yield new biochemical insight(s) into indirect Ag presentation by class II molecules. A mechanistic understanding of class II-restricted indirect Ag presentation is critical not only for developing ways to circumvent/treat GvHD but also for vaccine design as this process is operative in the presentation of cytosolic Ags (viral, bacterial, parasitic) to TH cells and, hence, for vaccine design against tumours and pathogens. !